Production of toluene



Patentedllune 27, 1944 PRODUCTION OF TOLUENE Vladimir N. Ipatieil and George 8. Monroe, Chicago, Ill., assignors-to Company, Chicago, 11].,

ware

Universal Oil Products a corporation of Dela- No Drawing. Application May 24, 1941, Serial No. 395,056

Claims. (Cl. 260-671) This invention relates to the production of toluene by interaction of benzene and methane in the presence of a catalyst. More specifically it is concerned with the conversion of benzene into substantial yields of toluene and diphe'nyl in the presence of a silica-containing catalyst.

It i recognized that benzene has been converted into toluene and more-highly methylated benzenes by treatment with methyl chloride in ,the presence of aluminum chloride catalyst. Methyl chloride so employed as a methylating agent must be prepared synthetically and is more expensive than methane, the relatively abundant gaseous paramn hydrocarbon utilized in the process of the present invention which employs a silica-containing catalyst to assist'in removing hydrogen and eilecting combination between benzene and methane.

of sodium silicate by the addition of an acid,

. eral, suitable hydroated silica may be produced In one specific embodiment the present inven- I tion comprises a process for producing toluene which comprises contacting benzene with methane at a temperature of from about 350 to about 750 C. in the presence of a synthetically prepared composite of silica and one or more of alumina, zirconia, and thoria.

Silica-containing catalysts suitable for use in the process of the present invention maybe prepared by anumber' of alternative methods which have certain features in common as will subsequently be described. Generally speaking; however,- the silica-containing methylating catalysts as referred to in this specification and in the claims, may be considered to comprise intimate combinations of silica with alumina, zirconia, and/or thoria all of which components possess more or less low activity individually but-display high activity in' the a gregation. This activity is not an additive function, as it is relatively constant for a wide range of proportions of the components whether in molecular proportions or fractions of molecular proportions. No one component may be determined as the one component for which the remaining components may be considered a the promoters according to conventional terminology, norcan any component be definitely stated to be the. support and the others the catalyst proper.

Y According to one general method of preparation the preferred silica-containing catalysts may be prepared by precipitating silica from solution as a hydrogel and subsequently admixing or depositing the hydrogels of alumina, zirconia. and/or thoria upon the hydrated silica. Oneoi' 1 the more convenient methods of preparing the silica hydrogel is to acidify an aqueous solution 'kali metal ions.

by the use of dilute solutions of sodium silicate and the addition of a moderate excess of acid whereby the desired active silica gel is obtained and conditions of filtering and washing are at an optimum.

After precipitating the silica hydrogel, it is treated and washed to substantially remove a1- It is not known whether) the alkali metal ions, such as sodium ions, are present in the primary gel in chemical combination, or inan adsorbed state but it has been determined definitely that their removal is necessary it catalysts are to be obtained suitable for prolonged use in accelerating hydrocarbon conversion reactions of the present character. It is possible that the presence of the alkali metal impurities causes a sinterin'g or fluxing of the surfaces of the catalyst at elevated temperatures so that the porosity ismuch reduced with corresponding reduction in eil'ective surface. Alkalimetal ions may be removed by treating th hydrated gel with solutions of acidic materials, am

monium salts, or salts of. aluminum, zirconium,

and/or thorium. When treating with acidsfias for example with hydrochloric acid, the acid extracts alkali metal impurities from the silica gel. The salts formed and acid are thensubstantially completely removed by water washing treatment. Where ammonium salts, or salts or aluminum, zirconium, and/or thorium are used, the ammonium or multivalent metals used apparently dis place the alkali metal impurities present in the composite and the alkali metal salts formed, tozether with the major portion of the multivalent salts, are removed in the water washing treatment. Some of ,the multivalent metals introduced into the silica hydrogel in-the purifying treatment may become a permanent part or the silica gel may be solution of aluminum, zirconium, and/or thorium salts in the desired proportion and the alumina,

- zirconia, and/or tho'ria hydrogeldeposited upon the suspended silica hydrogel by the addition of volatile basic precipitants; such as ammonium hydroxide, ammonium carbonate, ammonium hydrosulfide, ammonium sulfide, or other materials,

such as organic bases may be employed. According to this method, the purified silica gel may be suspended in a solution or aluminum chloride, zirconyl nitrate, and/or thorium nitrate, for example, and the hydrated alumina, zirconia, and/or thoria precipitated by the addition or ammonium hydroxide; In this example, the alumina, zirconia, and/or thoria are co-precipitated.

Alternatively the purified silica gel may be mixed while in the wet condition with separately prepared hydrated alumina, hydrated zirconia, and/or hydrated thoriav precipitated either separately or concurrently, as forexample by the addition of volatile basic precipitants to solutions of aluminum, The hydrated alumina, hydrated thoria thus prepared are substantially free from alkali metal ions and can be mixed with purified silica gel. However, it alkali metal ions are incorporated as when the hydrated alumina is prepared from sodium aluminate, for example, or if zirconium and/orthorium tetrahydroxides are precipitated by the interaction of zirconyl nitrate and/or thorium nitrate and sodium hydroxide, regulated and water washing, by methods selected from those described in connection with the purification of hydrated silica gel to remove alkali metal ions, will be required. Care should be observed in the selection of. alumina, zirconia, and/or thoria.

As further alternative proceeding in the preparation of the preferred methylating catalysts purified silica gel may be added to a solution of salts or aluminum, zirconium, and/or thorium thoria prior to thedrying treatment. In methv odsdescribed below, the hydrated silica with a hydrated alumina. hydrated zirconia, and/or bydratedthoria are concurrently precipitated or admixed and treated" to remove the alkali metal ions from the. composlted material prior to drying inthe presence of the originalreactants or subsequent to water washing, Thus,

' solutions of silicon compounds, more usually al-- 'kali metal silicates and soluble aluminum, zirconium, and/or thorium salts maybe mixedun-- .der regulated conditions of acidity or basicity hydrated silica, hydrated alumina, hydrated zirconia, and/or hydrated to :1 ointly precipitate thoria in varying proportions. For example, solutions or sodium-- silicate, aluminumchloride,

zirconyl nitrate, and/or thorium nitrate purification treatment and/ or thorium;

zirconium, and/or thoriumsalts. hydrated zirconia, and/or and concentration of reagents used so as not to dissolve unduly large amounts scribed gssaaoo mixed and an alkaline or acid reagent added according to the proportions used so that in the mix a pH in the range of about 3 to about 10 is obtained. In cases where a sol is formed, the precipitation may be brought about if the sol is acid by the addition of a volatile base, as for example, ammonium hydroxide, and alkali metal salts may be removed by water washing, or the composite may be treated as indicated above in'connection with the purification of the hydrated silica to remove alkali metal ions. Various methods are possible-for the preparation of the hydrated silica, hydrated alumina, hydrated zirconia, and/or hydrated thoria separately or in combination and the purifying treatment is always necessary where alkali metal ions are present in substantial amounts.

Thecharacter and efilciency of the ultimately prepared silica-containing catalysts vary more or less with methods of precipitation and/or mixing, purification treatment, ratio of components, calcining, etc. The ratio of the components may be varied within relatively wide limits, the limiting factor being more in evidence 'with respect to small proportions than with large proportions of the various components. In general, it appears that irom 2 to about 6 mole per cent of alumina, zirconia, and/or thoria together with reference to'silica may be considered an approximation of the minimum proportions.

After the alumina, zirconia, and/or thoria have been mixed with or deposited on the -purified silica gel .and water washed, if desired, as defor one general method of preparation, or afterthe hydratedsilica, hydrated alumina, hydrated zirconia, and/orhydrated thoria have been composited and treated to remove the alkali metal ions, as described for another general may be recovered as a filter cake and dried at a temperature in the order of 115 to 150 C., more or less, after which they may be'formed into particles of a suitable average definite size ranging from powder to particles of various forms and sizes obtained by pressing and screening,- or otherwise formed into desirable shapes by compression or extrusion methods.

By calcining at temperatures of the order of approximately 450 to 550 0., maximum activity of the silica-base catalyst is obtained and a further dehydration occursv so that, for example, after a considerable period of heating at 500 C., the water content, as determined by analysis, is of the order of 2 to 3%.

Silica-containing methylating catalysts preared by the various types of procedures outlined above evidently possess ,large total contact surfaces corresponding to a desirable porosity, the pores of the catalyst particles being of such size and shape that they do not readily become clogged with carbonaceous deposits after a long period or service and are, therefore, not particu: larly difilcult'to reactivate by oxidation. This structure is retained, also, after many alternate periods or use and reactivation, as evidenced by the fact that the catalysts may be reactivated if rapidly by passing air or other oxidizing gas over I the used particles to burn, off the deposits of 425 C., temperatures as ing the catalytic activity.

at temperatures above high as 750 to 900C.

affectcarbonaceous materials having been reached, without apparently In carrying out the reaction between benzene and methane according to the process or the may be present invention the exact methodotprocedure 7 method of preparation, the catalytic materials or higher, the l and operating conditions employed Vary with the proportions of the reacting constituents as well as with the composition and activity of the catalyst employed. The different catalysts which may be employed are thus not necessarily equivalentin their action. a

The procedure preferably utilized for effecting methylation of benzene according to the process of this invention consists in passing-a mixture of benzene and a molar excess of methane over a fixed bed of one of the herein described silicacontaining catalysts maintained at a temperature of from about 350 to about 750 C. under a pressure of from about 50 to about 450 atmospheres. The reaction mixture undergoing treatment preferably contains between about 2 and about 20 molecular propo ons of methane per 1 molecular proportion o benzene in order to favor production of toluene and to diminish the reactions which result in formation of diphenyl and of alkylated diphenyl, both of which are .valuable products although not the preferred products of the present process.

While the method of passing methane and benzene either together or countercurrently through a suitable reactor containing a fixed bed of silica-containing methylating catalyst is generally customary procedure, interaction of methone and benzene may also be effected in batch type of operation in which the catalyst is present in finely divided form and is preferably maintained in dispersion or suspension by some means of agitation.

In general the products formed during treatment of mixtures of benzene and methane with a silica-containing catalyst are separated from unreacted benzene and methane by suitable means as by distillation and the unreacted portions-oi the benzene and methane are recycled and commingled with additional quantities of these hydrocarbons being charged to contact with -the catalyst. Hydrogen or hydrogen-contalning gases produced in the process may also be recycledwith' the recovered benzene and methane. The reaction'product boiling higher than benzene is separated into desired fractions or individual compounds including toluene and diphenyl by distillation at ordinary or reduced pressure or by other suitable means. From the reaction products it is also generally possible to separate certainamounts of more-highly methylated benzenes and some alkylated di-phenyl derivatives;

The following examples are given to illustrate the character of*res1i1ts obtained by the use of the present process, although the data presented are not introduced with the intention of unduly limiting the generally broad scope of the inven tion. 7

EXAMPLE I 75.5 parts by weight of. 3 x 3. mm. pellets, formed by pelleting and calcining a composite of 100 molecular proportions of precipitated silica and molecular proportions of alumina, was used as a filler in a steel reactor through which a mixture of 8 molecular proportions of methane and 1 molecular proportion of benzene was passed in three {runs at temperatures of 501, 540 and 564 C., respectively, under 234 atmospheres pressure at rates necessaryfor an average time of contact between about 190 and 200 seconds. In these runs the benzene was charged at an hourly rate corresponding to approximately 0.37 vol- .unfe or liquid per volume of catalyst. The liquid reaction products were obtained in admixture with unreacted benzene equivalent to between 79 and 87% by weight of that charged. Upon the basis of the weight of benzene consumed in these conversion reactions the yields of toluene, higher alkylated benzenes, anda higher boiling residue rionslisting largely of diphenyl are shown in a eI.

A similar run at 509 C. under under 290 atmospheres pressure in which the methane: benzene ratio was 10, eliected 10.4% conversion of the benzene into heavier products. Upon-the basis of the benzene consumed, the respective yields of toluene, higher alkylated -.-'produc.ts (probably containing xylenes) and diphenyl .residue were 19.1%, 14.5 and 14.5%. increasex in pressure in this run over that used in run #1 shown above decreased the toluene yield but increased the formation of higher boiling 'alkylated.

aromatics, while the formation of diphcnyl residue remained about constant.

Toluene was thus produced by the, simultaneou's contact of benzene and methane witha silica-containing catalyst at the relatively high. temperatures and pressures herein-indicated. A run made in the absence of methane charging.

benzene at a rate sufficient to give an average contact time of approximately 217% seconds yielded smaller amounts of toluene and larger amounts ofdiphenyl than obtained in the present runs. Approximately 12% by weight of the benzene so passed over the silica-alumina catalyst underwent:v conversion. Upon the basis of the weight of benzene consumed the respective yields of toluene, higher methylated .ibenzenefs. and dlphenyl residue were 5.5%, 33%, and- 77.6%. Another run in which methane valone.

was subjected to a similar temperature .of about 579 Ctfor a contact time of 208seconds yielded no liquid product. ExAmrti: II

Simultaneous passage of 9 molecular proportions of methane and 1 molecular proportion or benzene through a steel reactor containing 79.8,

parts by weight of pellets, formed from 8 molecular proportions of alumina and molecular proportions of silica, maintained at 570 C. under 2 34 atmospheres pressure effected-20% comer-=- sion of the benzene treated. Upon the basisof the benzene converted the respective yields; of

toluene. higher alkylated products, and diphenyl residue were 18.7%, 1.3%, and 12.9%.

Y EXAMPLE III Severalruns were madein which benzene was contacted with methane at an average temperadifierent runs are shown in Table II:-

curred also inru'nj in which benzene was. eonanother hydrated oxide, to efi' t interaction of said benzene and said methane.

' sting conditions in the presence of a synthetically Ru'n No.

Length oirun,hrs .L 2.0 2.0 4.0 2.0 3.5

-Chsrge, moles of methane/mole oibcnlene 7. 79 9.1 8.3 3.0 3.7 Charging rate, space velocity:

Bcnrene (as quid) 1.60 0.00 0.38 0.88 0.46 Methane (gas) 3,12) 1,466 770 780 715 Av etime oi contact seconds- 103 197 201 241 Liqui hydrocarbons recovered, L

per cent by wt. of benzene charged: Bensene 88.2 83.5 78.0 85.8 81.2 Toluene 2. 2 4. 1 4. 2 3. 2 3. 4 Higher benzene hydrocarbons..---; 1.2 0.9 0.4 1.7 2.2 I Di mlresidue [3.1 2.0 3.0 4.5 4.2 Liqui p nets recovered, per

cent by wt. of benzene consumcd: I 'ifli i ene 18.5 24.9 19.0 2.7 17.9

H mm ydm- 10.4 5.5 2.0 12.0 11.0 -,Diphenylresidue 20.4 17.1 14.0 81.4' 42.3

I Methane charged contained per cent byvoiume of hydrogen. In the above indicated runs the optimum yield and methane to contact at a temperature of from about 350 to about 750 C. in the presence of a.

assaaoo of toluene which comprises and methane to contact at a temperature of from I about 350' to about-750' C; in the presence of a synthetically prepared catalyst formed by calcin- 5 ing a composite comprising hydrated silicon oxide, I

and methane to contact at a temperature of from 10 about 350 to about 750 C. in the presence of a synthetically. prepared catalyst formed by calcining a composite comprising hydrated silicon oxide and a hydrated oxide of zirconium.

' 5. A process for producing .a substantial Yield oi toluene which comprises subjecting benzene synthetically prepared catalyst formedby calcininga composite comprising hydrated silicon oxide and a hydrated oxide of thorium. I

6. A processdor producing a substantialyield of toluene which comprises subjecting benzene C and methane to contact at a temperature of from about 350 to about 750 C. under a pressure between about 50 .and about 450 atmospheres in the oi toluene was obtained under the conditions of presenoe of synthetically prepared run #2 in which the average time oi. contact with the catalyst was approximately 103 seconds. However, the traction of xylene boiling range andthe diphenyl residue both formed in" greater proportions at a contact time of 58 seconds than 0 at the much longer contact time or 197 seconds. Run #4 was made with the chargingratio of methane to benzene at about 3.6. Apparently ,the I total production of aromatic hydrocarbons exclusive or diphenyl was about the same as when the methane-benzene ratio was about 8, but there was also-a tendency tor an increase in production oia'xylcne fraction at the expense of toluene yield. About 30% of the benzene consumed was converted into.diphenyl and related high molecular weight aromatic hydrocarbons.

Substantial formation of toluene and of a higher boiling benzene hydrocarbon fraction octacted with a methane-hydrogen mixture containingabout. 10% by volume of the latter.

The character "of the process of the present invention and particularly its commercial value are evident from the preceding speciiication and examples given, although neither section is in- 1 tended to unduly iimit its generally broad scope.

2. A process for producing a substantial yield =oi toluene which comprises subjecting a mixture of benzene and methane to contact under alkylprepared catalyst i'ormedby calcining a compos'ite'comprising hydrated silicon oxide and a hydrated oxide ohiluminum;

' s 3. A-process for producing a substantial yield 7 I formedby calcining a composite comprising esand zirconium.

7. A process for producing a substantial yield of toluene which comprises subjecting benzene and methane to contact at'a temperature 0! from about 350 to about 750 C. under a pressure between about 50 and about 450 atmospheres in the presence of a synthetically. prepared catalyst formed by calcining a composite comprising essentially hydrated oxides of silicon, aluminum, and thorium. 7 I

8.- A process for producing a substantial yield of toluene which comprises subjecting benzene and methane to contact at a temperature of from about 350 to about 750 C. under a pressure between about 50 and about 450 atmospheres in the presence of ,a synthetically prepared catalyst i'ormedby calcining a composite comprising e'ssentiaily hydrated oxides of silicon and aluminum.

. 9. A process ior producing a substantial yield of toluene which comprisesrsubiecting 1 molecule!" proportion of benzene-and between about 2 and so about 20 molecular proportions of methaneto contact at .a temperature of from about 350 to about 750 C. under a pressure between about and about 450 atmospheres in the presences! e synthetically prepared catalyst formed by calcinss ing a composite comprising essentiallyhydratedoxides of silicon, aluminum, andzlrconium.

10. A process for producing a-substantial yield oi toluene which comprises subjecting 1 molecular proportion of benzene and between about 2 and go about 20' moietular proportions of methane to contact at a temperature of from about 350 to about 750 C. under apressure-between about 50 and-about 450 atmospheres in the presence of a synthetically prepared catalyst formed by .palcines ing a composite comprising essentially hydrated oxides of silicon and aluminum.

" mrm'ims. j aroma a. Mormon.

subjecting benzene 

